B757-200 PLT RPTR EXPERIENCES 30-40 DEG UNCOMMANDED ROLL JUST PRIOR TO TOUCHDOWN.

Narrative

A NORMAL APCH TO LNDG WAS ACCOMPLISHED TO ORD RWY 14R. WINDS WERE RPTED AS 190 DEGS/24-26 KTS (NO GUST) AND THE ATIS STATED THAT ACFT WERE DEPARTING RWY 27L. DURING THE LNDG PHASE AT 50 FT AGL; THE ACFT BEGAN A RAPID ROLL TO THE L. THE FO (PF) APPLIED CORRECTIVE ACTION FOLLOWED BY RAPID ROLLS TO THE R AND L. THE ROLLING TENDENCY CEASED ABRUPTLY AND A NORMAL TOUCHDOWN WAS ACCOMPLISHED. THE CABIN CREW AND PAX WERE VERY CONCERNED. THE TWR WAS NOTIFIED OF POSSIBLE WINDSHEAR; ALTHOUGH THE FO STATED THAT IT FELT LIKE WAKE TURB. IN THE FUTURE; I WILL MAKE A PA TO EXPLAIN THE CAUSE OF THIS TYPE OF OCCURRENCE; ALTHOUGH I AM STILL NOT SURE WHY IT HAPPENED. THIS SIT OCCURRED JUST AS I (PNF) GLANCED INSIDE TO MAKE THE REQUIRED COMPANY ALT CALLOUTS. SOME ACFT HAVE AUTOMATED ALT CALLOUTS (A320) WHILE OTHERS HAVE THE SO (FE) MAKE THE CALLS. ON A 2 PLT ACFT; CALLOUTS MADE BY THE PNF TAKES THAT PLT OUT OF THE LOOP WHEN HE SHOULD BE LOOKING OUTSIDE; ESPECIALLY WHEN THE ACFT IS THAT CLOSE TO THE GND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS RPTR PARTICIPATED IN THE STRUCTURED CALLBACK PROGRAM FOR WAKE TURB. RPTR STATED THAT THE SUDDENNESS OR THE UNEXPECTEDNESS OF THE JOLT IS WHAT CAUSED SO MUCH EMOTIONAL TRAUMA. PAX WERE UPSET AND ALTHOUGH IT WAS NOT OF LONG DURATION; IT CAUSED THE ACFT TO LAND FIRMLY WHICH ADDS TO THE PAX ANXIETY. RPTR WAS NOT THE PF UNTIL THE WAKE HIT THE ACFT; THEN HE; AS CAPT; TOOK OVER THE CTLS. RPTR FELT THE TURB WAS GENERATED FROM ACFT DEPARTING RWY 27L AND THE S WIND BLOWING IT OVER TO THEIR ARR AREA. SUPPLEMENTAL INFO FROM ACN 321159: RWY 14R; THE B757 MADE AN UNCONTROLLED/COMMANDED ROLL. THE ROLL HAPPEN JUST AFTER THE 50 FT (RA) CALLOUT BY THE CAPT (PNF). THE LAST RPTED WINDS AT THE TIME WERE 190 DEGS AT 24-26 KTS RPTED BY ORD TWR. I USED THE FULL ROLL CTL CORRECTION TO THE R TO STOP THE ROLL. IT IS MY FIRM BELIEVE IF FULL ROLL CTL WAS NOT USED THE ACFT WOULD HAVE MADE CONTACT WITH THE GND; OTHER THAN LNDG GEAR FIRST. THIS HAPPENED SO QUICKLY THAT THERE WAS NOT TIME TO GAR AND WE FLEW OUT OF THIS; WAKE TURB OR WINDSHEAR QUICKLY. THE ACFT MADE A SAFE LNDG WITH NO DAMAGE TO ACFT. ATIS AT ORD DID RPT THAT DEPS WERE TAKING PLACE OFF RWY 27. THE FLT WAS OPERATING UNDER ALL FARS AND ALL COMPANY PROCS WERE BEING FOLLOWED. CALLBACK CONVERSATION WITH RPTR OF ACN 321159 REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING THE B757 MODEL 200. THE UNCOMMANDED 30-40 DEG ROLL NEAR TOUCHDOWN EXPERIENCE REMAINS A MYSTERY. HE CANNOT THINK OF ANYTHING HE COULD DO DIFFERENTLY. NOR CAN HE THINK OF ANY CTLR'S PROCS OR OTHER PROCS THAT SHOULD BE CHANGED. NEVERTHELESS; THERE WAS A MOMENT WHEN THE CAPT AND FO THOUGHT THEY HAD LOST CTL AND THE WING WAS GOING TO STRIKE THE GND. SOME PAX AFTER THE FLT AS THEY WERE COLLECTING THEIR BAGGAGE WERE HEARD BY COMPANY PAX AGENTS TO COMPLAIN TO THE EXTENT THEY WERE GOING TO CALL THE FAA ('THE WORST LNDG I HAVE EVER HAD!'). ON LNDG SOME OF THE PAX LITERALLY CLAPPED FOR THE MANNER IN WHICH THE CREW RECOVERED CTL. THE TOUCHDOWN WAS FIRM BUT NOT HARD. (ON A SCALE; 1 BEING HARD AND 10 BEING A ROLLER; THE TOUCHDOWN WAS ABOUT A 5.) SOME FLT ATTENDANTS COULD NOT FLY THE NEXT DAY. THE WINDS AT 5000-6000 FT WERE OBSERVED ON THE FMC -- IRS TO BE SOUTHERLY (160-210 DEGS) AT 60-70 KTS. AT THAT TIME OF THE NIGHT THERE WERE LIMITED RWYS OPEN. ATIS WAS ADVERTISING LNDG ON RWY 14R AND DEPARTING RWY 27 WITH WINDS 190 DEGS AT 24-26 KTS. B757 GND SENSING HAS A HISTORY OF MALFUNCTIONS. THE RPTR HAD THE R ENG GO TO FLT IDLE ON A START ONE TIME WHEN THE LOGIC IS IT IS SUPPOSED TO GO TO GND IDLE. THERE HAS BEEN AT LEAST ONE INCIDENT IN WHICH THE SPOILERS DEPLOYED BEFORE TOUCHDOWN WHEN THE THROTTLE WAS RETARDED TO IDLE. THERE IS A CAUTION IN THE MANUAL THAT THE SPOILERS WHEN ARMED MAY DEPLOY WHEN THE FLAPS ARE MOVED FROM FLAPS 25-30 DEGS. THE FLAPS WERE ALREADY AT 30 DEGS SINCE ABOUT 1000 FT AGL IN THIS CASE.